The present invention relates to a transmission arrangement for a vehicle. The invention also relates to a vehicle comprising such a transmission arrangement. The invention is applicable on vehicles, in particularly working machines such as e.g. wheel loaders, articulated haulers, dump trucks, etc. Although the invention will mainly be described in relation to an articulated hauler, it may also be applicable for other type of vehicles such as e.g. trucks.
In connection with transportation of heavy loads at construction sites or the like, a working machine is often used. The working machines may be utilized for transportations in connection with road or tunnel building, sand pits, mines, forestry and similar environments. Thus, the working machine is frequently operated with large and heavy loads in rough terrain and on slippery ground where no regular roads are present.
In order to fulfil the desired demands from the fields where the working machine is frequently operated, high quality of the vehicle gearbox is necessary. The gearbox is arranged for adjusting the speed and tractive effort of the vehicle in dependency of the specific driving scenario. The gearbox comprises a transmission arrangement and depending on the specific type of gearbox, the transmission arrangement may comprise e.g. ordinary gear sets with cylindrical gear wheels in meshed connection with each other or planetary gear sets comprising a respective sun gear, ring gear and a planet carrier, or a transmission arrangement having a combination of ordinary gear sets and one or more planetary gear sets.
SE 527 108 describes a vehicle transmission arrangement, particularly suitable for working machines. The transmission arrangement in SE 527 108 comprises an input shaft and an output shaft. Five planetary gear sets are arranged between the input shaft and the output shaft for providing the desired gear ratios. Also, the transmission arrangement comprises three clutches and five brakes for achieving the desired gear shifts. Hereby, nine forward gears and four reverse gears are provided for the transmission arrangement in SE 527 108.
Although the transmission arrangement in SE 527 108 provides for a sufficient number of gears, the transmission arrangement is still in need of further improvements in terms of costs and functionality.
It is desirable to provide a transmission arrangement that comprises fewer components and has an improved gear shiftability in comparison to the prior art.
According to a first aspect of the present invention, there is provided a transmission arrangement for a vehicle, the transmission arrangement comprising a first, a second, a third, and a fourth planetary gear set comprising a sun gear, a planet carrier and a ring gear, respectively, wherein said transmission arrangement further comprises a transmission housing, an input shaft and an output shaft, wherein the planet carrier of the first planetary gear set and the output shaft are operatively connected to each other; the ring gear of the first planetary gear set and the planet carrier of the second planetary gear set are operatively connected to each other; the sun gear of the first planetary gear set and the sun gear of the second planetary gear set are operatively connected to each other; the ring gear of the second planetary gear set and the planet carrier of the third planetary gear set are operatively connected to each other, and two of the sun gear, the planet carrier and the ring gear of the fourth planetary gear set are each operatively connected to a respective one of the input shaft, the sun gear, the planet carrier and the ring gear of the third planetary gear set.
The wording “operatively connected to” should in the following and throughout the entire description be interpreted such that the components thereof are fixedly connected to each other, i.e. the rotational speed of the components which are operatively connected to each other is the same. Hence, no connecting mechanism or the like is arranged between the components that are operatively connected to each other and they can therefore not be disengaged from one another during operation. Accordingly, the planet carrier of the first planetary gear set is always connected to the output shaft of the transmission arrangement.
Furthermore, it should be readily understood that the wording “two of the sun gear, the planet carrier and the ring gear of the fourth planetary gear set are each operatively connected to a respective one of the input shaft, the sun gear, the planet carrier and the ring gear of the third planetary gear set” implies that one of the members of the fourth planetary gear set, i.e. the sun gear, the planet carrier or the ring gear, is operatively connected to one of the members of the third planetary gear set or to the input shaft of the transmission arrangement. At the same time, another one of the members of the fourth planetary gear set is operatively connected to another one of the members of the third planetary gear set or to the input shaft of the transmission arrangement.
The advantages of the present invention is that, in comparison to the prior art, only four planetary gear sets are used in order to obtain a sufficient number of forward and reverse gears. This is advantageous both in terms of cost and packaging of the transmission arrangement since the number of components reduces the total cost for the transmission arrangement at the same time as it will be easier to fit the transmission arrangement to a vehicle. The engine compartment is an environment where it often is desirable to reduce the size of the components housed therein and the present invention hence reduces the size of the transmission arrangement by having one less planetary gear set in comparison to the prior art.
Moreover, by means of the present invention, nine forward gears and three reverse gears are obtainable, where the ratios and the steps for the different gears are considered to be able to appropriately operate e.g. a working machine to provide sufficient speed when necessary and sufficient torque when necessary. The ratio and step for the different obtainable gears will be described further below in relation to the detailed description of the present invention.
A still further advantage is that further additional gears and alternative gears relative to the nine forward gears and the three reverse gears described above are obtainable. For example, an additional forward gear and an additional reverse gear are obtainable by means of the present invention. Also, three alternative forward gears and four alternative reverse gears are obtainable by means of the present invention. These additional gears and alternative gears will also be described further below in relation to the detailed description of the present invention.
According to an example embodiment of the present invention, the planet carrier of the second planetary gear set may be selectively connectable to the ring gear of the third planetary gear set. According to an example embodiment, the transmission arrangement may comprise a first connecting mechanism for selectively connecting the planet carrier of the second planetary gear set to the ring gear of the third planetary gear set. The first connecting mechanism may, for example, be a clutch arrangement, such as e.g. a wet or dry friction disc clutch. Other alternatives are of course also conceivable.
The wording “selectively connectable to” should in the following and throughout the entire description be interpreted as an element being connectable at desirable points in time to another element. Hereby, gear shifts of the transmission arrangement can be executed by either connecting or disconnecting elements to/from each other. Components may be selectively connectable to each other by means of connecting mechanisms and controlled by e.g. a control unit or the like. When a connecting mechanism is positioned in an engaged state the components are connected to each other.
According to an example embodiment of the present invention, the sun gear of the third planetary gear set may be selectively connectable to the planet carrier of the second planetary gear set and the ring gear of the first planetary gear set. According to an example embodiment, the transmission arrangement may comprise a second connecting mechanism for selectively connecting the sun gear of the third planetary gear set to the planet carrier of the second planetary gear set and to the ring gear of the first planetary gear set. The second connecting mechanism may, for example, be a clutch arrangement, such as e.g. a wet or dry friction disc clutch. Other alternatives are of course also conceivable.
Hereby, the second planetary gear set has well defined connections to the first and third planetary gear sets.
According to an example embodiment of the present invention, the ring gear of the third planetary gear set may be selectively connectable to the transmission housing. According to an example embodiment, the transmission arrangement may comprise a first locking mechanism for selectively locking the ring gear of the third planetary gear set to the transmission housing. The first locking mechanism may, for example, be a brake arrangement, such as e.g. a wet or dry friction disc brake. Other alternatives are of course also conceivable.
Accordingly, the ring gear of the third planetary gear set can hence be locked to the transmission housing such that the ring gear is prevented from rotating.
According to an example embodiment of the present invention, the planet carrier of the second planetary gear set may be selectively connectable to the transmission housing. According to an example embodiment, the transmission arrangement may comprise a second locking mechanism for selectively locking the planet carrier of the second planetary gear set to the transmission housing. According to an example embodiment, the second locking mechanism may be designed as a dog clutch. Other alternative locking mechanisms are of course also conceivable, such as a wet or dry friction disc brake, etc.
By using a dog clutch design, a durable locking arrangement is provided which is not exposed to friction forces in the same way as a friction disc brake. Hereby, lower drag losses occur when the locking mechanism is disengaged. Accordingly, the planet carrier of the second planetary gear set can be locked to the transmission housing such that the planet carrier is prevented from rotating.
According to an example embodiment of the present invention, the sun gear of the second planetary gear set and the sun gear of the first planetary gear set may be selectively connectable to the transmission housing. According to an example embodiment, the transmission arrangement may comprise a third locking mechanism for selectively locking the sun gear of the second planetary gear set and the sun gear of the first planetary gear set to the transmission housing. The third locking mechanism may, for example, be a brake arrangement, such as e.g. a wet or dry friction disc brake. Other alternatives are of course also conceivable.
Hereby, the sun gear of the second planetary gear set and the sun gear of the first planetary gear set can be locked to the transmission housing such that rotation thereof is prevented.
According to an example embodiment of the present invention, the stationary gear ratio of each one of the first, second and third planetary gear sets may be negative. An advantage is that single planet wheels are used, which reduces cost and gear mesh losses.
According to an example embodiment of the present invention, the sun gear of the fourth planetary gear set may be operatively connected to the ring gear of the third planetary gear set; and the ring gear of the fourth planetary gear set may be operatively connected to the sun gear of the third planetary gear set. According to an example embodiment of the present invention, the input shaft may be selectively connectable to the ring gear of the fourth planetary gear set and the sun gear of the third planetary gear set and selectively connectable to the planet carrier of the fourth planetary gear set. According to an example embodiment of the present invention, the transmission arrangement may comprise a third connecting mechanism for selectively connecting the input shaft to the ring gear of the fourth planetary gear set and to the sun gear of the third planetary gear set, and a fourth connecting mechanism for selectively connecting the input shaft to the planet carrier of the fourth planetary gear set. Throughout the description, the third and fourth connecting mechanisms may, for example, be clutch arrangements, such as e.g. a respective wet or dry friction disc clutch. Other alternatives are of course also conceivable.
The transmission arrangement comprises four connecting mechanisms and three locking mechanisms, i.e. a reduced total number of connecting and locking mechanisms in comparison to the prior art. Also, since both the third and fourth connecting mechanisms are connected to the input shaft, oil supply to each of these connecting mechanisms may be provided through the input shaft.
According to an example embodiment of the present invention, the planet carrier of the fourth planetary gear set may be operatively connected to the input shaft; and the sun gear of the fourth planetary gear set may be operatively connected to the ring gear of the third planetary gear set. According to an example embodiment of the present invention, the sun gear of the third planetary gear set may be selectively connectable to the input shaft and selectively connectable to the ring gear of the fourth planetary gear set. According to an example embodiment of the present invention, the transmission arrangement may comprise a third connecting mechanism for selectively connecting the input shaft to the sun gear of the third planetary gear set, and a fourth connecting mechanism for selectively connecting the ring gear of the fourth planetary gear set to the sun gear of the third planetary gear set.
The transmission arrangement comprises four connecting mechanisms and three locking mechanisms, i.e. a reduced total number of connecting and locking mechanisms in comparison to the prior art.
According to an example embodiment of the present invention, the input shaft may be operatively connected to the planet carrier of the fourth planetary gear set; and the ring gear of the fourth planetary gear set may be operatively connected to the sun gear of the third planetary gear set. According to an example embodiment of the present invention, the sun gear of the fourth planetary gear set may be selectively connectable to the input shaft and the planet carrier of the fourth planetary gear set and selectively connectable to the ring gear of the third planetary gear set. According to an example embodiment of the present invention, the transmission arrangement may comprise a third connecting mechanism for selectively connecting the sun gear of the fourth planetary gear set to the input shaft and the planet carrier of the fourth planetary gear set, and a fourth connecting mechanism for selectively connecting the sun gear of the fourth planetary gear set to the ring gear of the third planetary gear set.
The transmission arrangement comprises four connecting mechanisms and three locking mechanisms, i.e. a reduced total number of connecting and locking mechanisms in comparison to the prior art.
According to an example embodiment of the present invention, the stationary gear ratio for the fourth planetary gear set may be negative. An advantage is that single planet wheels are used also for the fourth planetary gear set, which reduces cost and gear mesh losses.
According to an example embodiment of the present invention, the planet carrier of the fourth planetary gear set may be operatively connected to the sun gear of the third planetary gear set; and the sun gear of the fourth planetary gear set may be operatively connected to the planet carrier of the third planetary gear set. According to an example embodiment of the present invention, the input shaft may be selectively connectable to the planet carrier of the fourth planetary gear set and the sun gear of the third planetary gear set and selectively connectable to the ring gear of the fourth planetary gear set. According to an example embodiment of the present invention, the transmission arrangement may comprise a third connecting mechanism for selectively connecting the input shaft to the planet carrier of the fourth planetary gear set and to the sun gear of the third planetary gear set, and a fourth connecting mechanism for selectively connecting the input shaft to the ring gear of the fourth planetary gear set.
The transmission arrangement comprises four connecting mechanisms and three locking mechanisms, i.e. a reduced total number of connecting and locking mechanisms in comparison to the prior art. Also, since both the third and fourth connecting mechanisms are connected to the input shaft, oil supply to each of these connecting mechanisms may be provided through the input shaft.
According to an example embodiment of the present invention, the planet carrier of the fourth planetary gear set may be operatively connected to the planet carrier of the third planetary gear set; and the sun gear of the fourth planetary gear set may be operatively connected to the sun gear of the third planetary gear set. According to an example embodiment of the present invention, the input shaft may be selectively connectable to the sun gear of the fourth planetary gear set and the sun gear of the third planetary gear set and selectively connectable to the ring gear of the fourth planetary gear set. According to an example embodiment of the present invention, the transmission arrangement may comprise a third connecting mechanism for selectively connecting the input shaft to the sun gear of the fourth planetary gear set and to the sun gear of the third planetary gear set, and a fourth connecting mechanism for selectively connecting the input shaft to the ring gear of the fourth planetary gear set.
The transmission arrangement comprises four connecting mechanisms and three locking mechanisms, i.e. a reduced total number of connecting and locking mechanisms in comparison to the prior art. Also, since both the third and fourth connecting mechanisms are connected to the input shaft, oil supply to each of these connecting mechanisms may be provided through the input shaft.
According to an example embodiment of the present invention, the stationary gear ratio for the fourth planetary gear set may be positive.
An advantage of having a positive stationary gear ratio for the fourth planetary gear set in combination with operatively connecting the sun gear of the third planetary gear set to the sun gear of the fourth planetary gear set, and operatively connecting the planet carrier of the third planetary gear set to the planet carrier of the fourth planetary gear set is that third and fourth planetary gear sets can be designed as a compound planetary gear set of Ravigneaux type. A Ravigneaux type compound planetary gear set may be more cost efficient and arranged in a more compact design compared to two separate planetary gear sets.
According to a second aspect of the present invention, there is provided a vehicle comprising a prime mover and a gearbox, wherein the gearbox comprises a transmission arrangement according to any of the above example embodiments described in relation to the first aspect of the present invention.
Effects and features of the second aspect of the present invention are largely analogous to those described above in relation to the first aspect of the present invention.
Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.